This invention relates to a process for dehydrogenating gaseous alkanes in the presence of steam and a catalyst comprising zinc aluminate, tin oxide(s) and platinum.
The dehydrogenation of gaseous alkanes to alkenes in the presence of steam and catalysts comprising zinc aluminate, tin oxide(s) and platinum is known and has been described in numerous patents, such as U.S. Pat. Nos. 4,902,849, 4,152,365 and 3,957,688. Generally, the catalyst preparation comprises the step of calcining alumina and zinc oxide (and preferably also tin dioxide), followed by impregnation of the formed zinc aluminate (preferably admixed with SnO.sub.2) with platinum and calcining. The prior art teaches the use of flame-hydrolyzed alumina (i.e., crystalline alpha- or gamma-alumina) in the preparation of zinc aluminate. Even though catalysts prepared by the prior art method are quite effective in alkane dehydrogenation processes, coke deposition on the catalysts remains an operational problem (because it requires frequent catalyst regeneration by heating in a free oxygen containing gas, such as air). The present invention is directed to the use of a catalyst composition which results in reduced coke formation in an alkane dehydrogenation process.